REVIEW article

Front. Toxicol., 29 September 2025

Sec. Food and Nutritional Toxicology

Volume 7 - 2025 | https://doi.org/10.3389/ftox.2025.1670769

Excessive alcohol consumption: a driver of metabolic dysfunction and inflammation

  • 1. Department of Nutritional Sciences, University of Connecticut, Storrs, CT, United States

  • 2. Department of Food and Nutrition, Keimyung University, Daegu, Republic of Korea

Abstract

With the increasing prevalence of alcohol-related diseases, expanding our understanding of the toxic effects of excessive alcohol consumption is critical for prevention and treatment of metabolic and inflammatory pathology. This review summarizes current knowledge on the metabolic dysfunction and inflammation caused by alcohol and their impact on the pathogenesis of alcohol-related liver disease (ALD), type 2 diabetes, cardiovascular disease, and obesity, and neurological damage. It highlights recent evidence that alcohol induces a cascade of reactive oxygen species (ROS)-mediated lipid peroxidation and nicotinamide adenine dinucleotide (NAD+) depletion, triggering mitochondrial dysfunction and metabolic imbalances in the liver, heart, pancreas, and brain. By integrating these mechanistic insights with emerging data on how disrupted lipid and glucose metabolism amplify immune dysregulation, the review underscores the interplay between metabolic and inflammatory pathways in exacerbating tissue injury across these organs. A deep understanding of these metabolic and inflammatory disruptions is therefore essential for developing novel therapeutic strategies, including metabolic and nutritional interventions, aimed at mitigating the health risks of excessive alcohol consumption.

1 Introduction

Excessive alcohol consumption is a major global health concern, responsible for an estimated 4.7% of all deaths in 2019, according to a new 2024 report from the World Health Organization (). It significantly contributes to the global burden of diseases, particularly liver disease, cardiovascular complications, and metabolic disorders. For the purposes of this review, “excessive alcohol consumption” refers to patterns of drinking that exceed public health guidelines, such as binge drinking (consuming four to five or more drinks on an occasion) or heavy weekly use (8–15 or more drinks per week for women and men, respectively), which can lead to health and safety risks (; ). The toxicity of alcohol and its metabolites disrupts metabolic processes across multiple organs by inducing oxidative stress and depleting nicotinamide adenine dinucleotide (NAD+) (). Acetaldehyde, a toxic metabolite of alcohol, binds to proteins in mitochondria or microtubules, leading to structural damage and metabolic dysfunction. Furthermore, this harmful drinking pattern induces the overproduction of reactive oxygen species (ROS), culminating in oxidative stress and inflammation. This inflammatory state is a critical factor in the development of not only alcohol-related organ diseases and senescence-associated diseases but also in the pathophysiology of alcohol use disorder itself (). Moreover, depletion of NAD+ levels due to alcohol oxidation can impair energy-generating pathways, including mitochondrial β-oxidation of fatty acids and the tricarboxylic acid (TCA) cycle, further exacerbating metabolic dysfunction (; ).

Understanding the pathways sensitive to alcohol exposure is pivotal for the development of effective strategies to protect against alcohol-related conditions. This review summarizes the metabolic and inflammatory dysfunctions and diseases associated with excessive alcohol consumption. This exploration of alcohol-mediated dysfunctions can help identify new therapeutic approaches to protect against alcohol-related diseases.

2 Ethanol metabolism and its toxic effects

2.1 Ethanol oxidation

The primary pathway for alcohol metabolism is the oxidation of ethanol to acetaldehyde, catalyzed by cytosolic alcohol dehydrogenase (ADH), a process requiring NAD+ as a cofactor (). Acetaldehyde, a highly toxic byproduct, is further oxidized to acetate by acetaldehyde dehydrogenase (ALDH), another NAD+-dependent reaction (Figure 1). This sequential ethanol oxidation by ADH and ALDH occurs primarily in the cytoplasm and mitochondria of hepatocytes, respectively. Acetate, the end product of ethanol oxidation, is released into the bloodstream and transported to various peripheral tissues, where it becomes acetyl coenzyme A (acetyl-CoA) by the action of acetyl-CoA synthetase (ACS) in the mitochondria. Acetyl-CoA serves as a key intermediate in several metabolic pathways, including the TCA cycle, fatty acid synthesis, and ketone body formation, depending on the energy demands and nutritional status of the cell ().

FIGURE 1

During chronic alcohol consumption or elevated blood alcohol levels, cytochrome P450 2E1 (CYP2E1), located in the endoplasmic reticulum (ER), utilizes nicotinamide adenine dinucleotide phosphate (NADPH) and oxygen to oxidize ethanol and generate ROS during this process (). More recent in vivo studies in murine models have confirmed that chronic alcohol intake upregulates CYP2E1, exacerbating oxidative liver injury (). ROS can damage mitochondrial DNA (mtDNA) by diffusing across mitochondrial membranes or through close contact between the ER and mitochondria, leading to oxidative modifications, such as base alterations (e.g., 8-oxo-2′-deoxyguanosine), single- and double-strand breaks, and cross-linking of mtDNA proteins ().

Another minor ethanol oxidative pathway is present in peroxisomes, where ethanol is metabolized by catalase, especially in conditions of elevated hydrogen peroxide, often associated with chronic alcohol consumption (). Also, non-oxidative ethanol metabolism occurs at the cellular level, although it is relatively minor. Fatty acid ethyl ester synthases catalyze the reaction between ethanol and fatty acids to form fatty acid ethyl esters (FAEEs), which can disrupt membrane integrity, induce inflammatory responses, and interfere with mitochondrial function (). Although the accumulation of FAEEs exacerbates liver inflammation and fibrosis, key features of alcoholic steatosis (), their overall contribution to alcohol metabolism is considerably insignificant compared to the oxidative pathways (Figure 1).

Excessive alcohol consumption results in cellular and systemic toxicity driven by acetaldehyde and ROS, which disrupt cellular processes, leading to oxidative stress, inflammation, and mitochondrial dysfunction. This cascade compromises cellular integrity and contributes to the progression of alcohol-related diseases (ALDs) through widespread tissue and organ damage.

2.2 Oxidative stress and cellular damage

A primary mechanism of alcohol-induced toxicity is the excessive generation of ROS during its metabolism. Ethanol is oxidized by ADH and CYP2E1 into acetaldehyde, which is subsequently converted into acetate by ALDH (). This process generates large amounts of ROS, overwhelming the cell’s antioxidant defenses and triggering oxidative stress (). The accumulation of ROS causes oxidative damage of lipids, proteins, and DNA, resulting in cellular dysfunction and tissue injury ().

The excessive production of ROS also depletes NAD+, disrupting the balance of the NAD+/NADH ratio, which is essential for cellular energy production and metabolic processes. Furthermore, in vitro cell culture studies have shown that ROS accumulation also activates enzymes such as NADPH oxidase-2 and cyclooxygenase-2, further exacerbating oxidative damage and cellular injury (; ). Additionally, alcohol impairs cells’ antioxidant defenses, particularly by depleting the levels of glutathione, a key antioxidant that neutralizes ROS (). This impairment exacerbates oxidative damage across major organ systems, such as the liver, brain, and cardiovascular system.

Another critical consequence of alcohol-induced oxidative stress is the repression of sirtuin 1 (SIRT1) activity, an NAD+-dependent deacetylase, which regulates inflammation and oxidative stress responses (; ). Indeed, an in vitro study using RAW 264.7 macrophages linked reduced SIRT1 activity by ethanol exposure to increased inflammation and metabolic dysfunction (). Taken together, these interconnected mechanisms, including ROS overproduction, NAD+ depletion, and SIRT1 repression, play a significant role in alcohol-related cellular and systemic damage.

The liver is the central organ responsible for most ethanol metabolism, primarily by ADH and CYP2E1, decreasing the NAD+/NADH ratio (). Elevated NADH levels inhibit fatty acid oxidation and promote lipogenesis by increasing levels of acetyl-CoA and malonyl-CoA (). Malonyl-CoA further inhibits carnitine palmitoyltransferase 1, blocking the transport and oxidation of fatty acids in mitochondria, leading to lipid accumulation and steatosis (). Also, ROS generated by CYP2E1 further intensifies oxidative stress, lipid peroxidation, and inflammation (), contributing to the progression of ALD from simple steatosis to alcoholic hepatitis and cirrhosis. Chronic alcohol consumption triggers progressive cycles of liver injury, repair, and scarring, ultimately leading to hepatic fibrosis, cirrhosis, and liver failure. The toxic byproducts of ethanol metabolism, such as acetaldehyde and ROS, damage liver cells and impair their ability to detoxify harmful substances, such as endotoxins and gut-derived bacteria (). As liver cells are exposed to sustained damage, their detoxifying capacity decreases, exacerbating systemic toxicity ().

2.3 Inflammation

Alcohol-induced oxidative stress triggers an inflammatory response in the liver, the primary site of alcohol metabolism and inflammation (). The breakdown of alcohol generates ROS and pro-inflammatory mediators, including cytokines and chemokines, which contribute to tissue damage and disease progression (). In the liver, Kupffer cells (resident macrophages) play a central role in mediating alcohol-induced inflammation. Gut-derived lipopolysaccharides (LPS) translocate to the liver due to increased intestinal permeability, activating toll-like receptor 4 (TLR4) on Kupffer cells. This activation proceeds via the MyD88-dependent signaling pathway, which culminates in the activation of the transcription factor nuclear factor kappa B (NF-κB). Activated NF-κB then translocates to the nucleus and promotes the transcription of pro-inflammatory cytokines, including tumor necrosis factor (TNF) and interleukin-6 (IL-6) (). This chronic inflammatory state, driven by cytokines and ROS, promotes the progression of ALD, fibrosis, and cirrhosis. Alcohol also activates the NOD-like receptor family pyrin domain containing 3 (NLRP3) inflammasome complex within these immune cells. This activation is triggered by endogenous signals stemming directly from alcohol-induced cellular stress, such as mitochondrial ROS overproduction and the release of damaged mitochondrial DNA (mtDNA) into the cytosol. The assembled NLRP3 inflammasome activates caspase-1, which in turn cleaves pro-interleukin-1β (pro-IL-1β) into its mature, highly inflammatory form, IL-1β, a critical mediator in ALD pathogenesis ().

Beyond the liver, ethanol metabolism significantly affects the gastrointestinal (GI) tract by disrupting the intestinal barrier and altering the gut microbiome. Although the liver is the primary site for ethanol metabolism, enzymes such as ADH and ALDH are also present in the intestinal mucosa (). Intestinal bacteria further contribute to ethanol metabolism, producing additional acetaldehyde, which damages intestinal cells by forming adducts with proteins and DNA. Both the small and large intestines are affected by these changes, leading to chronic inflammation, disruption of tissue homeostasis, and eventual organ dysfunction (). Chronic ethanol consumption also results in gut dysbiosis, an imbalance between beneficial and pathogenic bacteria (). This imbalance, coupled with excessive acetaldehyde production, exacerbates inflammation in the GI tract. As ethanol metabolism progresses, tight junction proteins such as claudins and occludins are downregulated, increasing the permeability of the intestinal mucosa, commonly known as a “leaky gut”. This increased permeability allows toxins and bacterial products, such as LPS, to enter the bloodstream, triggering systemic inflammation (). Recent in vivo animal studies have further established this mechanism also disrupts mucosal immune defenses, suppressing Paneth cells that produce antibacterial compounds, leading to bacterial overgrowth, which intensifies inflammatory responses in the intestine and liver ().

Alcohol further disrupts the gut barrier by reducing protective molecules like intestinal trefoil factor and increasing ROS production, which weakens the epithelial lining (). Moreover, alcohol reduces the production of short-chain fatty acids (SCFAs) (), including butyrate, which exacerbates gut permeability and systemic inflammation, linking alcohol consumption to diseases in other organs, particularly the liver (). This allows harmful substances to infiltrate the bloodstream, amplifying systemic inflammation. Additionally, chronic alcohol exposure impairs vitamin metabolism, such as thiamine (vitamin B1), leading to deficiencies such as Wernicke-Korsakoff syndrome, which causes cognitive impairment (). These interconnected mechanisms underscore the significant impact of alcohol on the gut-liver axis and its contribution to the progression of ALD and other alcohol-induced pathologies.

2.4 NAD+ metabolism and cellular energy disruption

NAD+ is required for ethanol oxidation by ADH and ALDH, but its continuous consumption during alcohol metabolism depletes cellular levels, disrupting redox balance and impairing other NAD+-dependent functions. NADH produced by ADH is transported into mitochondria through the α-glycerophosphate or malate-aspartate shuttles for re-oxidation (; ), a process that supports NAD+ regeneration (). The efficiency of these transporters and the capacity of the mitochondrial respiratory chain to oxidize NADH determine the rate of ethanol oxidation and the cell’s ability to maintain redox homeostasis. We reported that alcohol depletes the cellular NAD+ pool and inhibits its synthesis. Alcohol inhibits the expression of nicotinamide phosphoribosyltransferase (NAMPT), the rate-limiting enzyme of the NAD+ salvage pathway, which was counteracted by an NAD+ precursor or a SIRT1 activator in ethanol-stimulated macrophages (; ; ). This inhibition, due to chronic alcohol consumption, exacerbates NAD+ deficiency in the liver and macrophages, further impairing metabolic functions, including fatty acid oxidation, glycolysis, and mitochondrial respiration, intensifying the metabolic imbalance and contributing to disease progression (; ).

The reduction in NAD+ also hinders the activity of SIRT1, which relies on NAD+ as a cofactor (). As SIRT1 activity declines, the regulation of key metabolic processes, such as DNA repair, oxidative stress response, and inflammation control, is disrupted, further intensifying the cellular damage caused by alcohol. This dysfunction contributes to increased oxidative stress, greater DNA damage, and chronic inflammation associated with long-term alcohol exposure ().

2.5 Mitochondrial dysfunction and dynamics

Mitochondria are crucial organelles responsible for energy production through oxidative phosphorylation. Alcohol metabolism severely impacts mitochondrial function by disrupting the NAD+/NADH balance and generating excessive ROS. Chronic alcohol consumption impairs mitochondrial oxidative phosphorylation, reducing ATP production and compromising the cell’s ability to generate energy efficiently (). Excessive ROS production in mitochondria damages mtDNA, proteins, and lipids, leading to impaired mitochondrial function. These oxidative modifications contribute to lipid peroxidation, protein dysfunction, and mtDNA mutations, further reducing mitochondrial energy capacity (). Alcohol also disrupts mitochondrial dynamics, which regulate fission and fusion processes (). Under normal conditions, these processes maintain mitochondrial health by removing damaged mitochondria through mitophagy and promoting content exchange to ensure functionality. However, alcohol promotes excessive mitochondrial fission and inhibits fusion, leading to mitochondrial fragmentation and impaired mitophagy (; ). Fragmented mitochondria are less efficient at energy production and more vulnerable to oxidative stress, which accelerates the decline in mitochondrial function ().

Our recent findings from an in vitro study in Kupffer cells indicate that chronic ethanol exposure activates the mitochondrial unfolded protein response (UPRmt), an adaptive mechanism designed to manage the accumulation of misfolded proteins within mitochondria (). Under normal conditions, UPRmt upregulates molecular chaperones and proteases to restore protein homeostasis (). However, prolonged ethanol exposure overwhelms this system, leading to further mitochondrial dysfunction. Notably, ethanol increases the nuclear translocation of activating transcription factor 5 and upregulates UPRmt-related genes in mouse Kupffer cells concomitantly with increased mitochondrial dysfunction.

3 Pathogenesis of alcohol-induced diseases

Excessive alcohol consumption disrupts metabolic processes far beyond the liver, leading to systemic dysfunctions that affect various organs. This disruption is primarily associated with lipid and glucose metabolism, resulting in metabolic imbalances that elevate the risk of conditions such as type 2 diabetes mellitus (T2DM), cardiovascular diseases (CVDs), and obesity. Alcohol’s impact on these pathways impairs insulin sensitivity, lipid metabolism, and energy balance, collectively driving the development and progression of these diseases. Figure 2 summarizes the systemic effects of chronic ethanol consumption, depicting its impact on multiple organ systems, including the brain, liver, pancreas, and musculoskeletal system, and its association with various diseases. Figure 3 presents the role of alcohol metabolism in metabolic and inflammatory disorders, detailing the disruption of lipid metabolism, intestinal barrier integrity, immune homeostasis, oxidative stress, and their downstream consequences leading to conditions such as obesity, T2DM, and ALD.

FIGURE 2

FIGURE 3

3.1 Alcohol-related liver disease (ALD)

ALD is a major cause of alcohol-related mortality and encompasses a spectrum of liver conditions, ranging from alcoholic fatty liver (AFL) to cirrhosis and hepatocellular carcinoma (HCC) (Figure 2) (). The progression of ALD is driven by chronic inflammation, oxidative stress, and metabolic dysfunction triggered by excessive alcohol consumption. The earliest stage of ALD is AFL, characterized by hepatic steatosis, or fat accumulation within hepatocytes (). This stage can progress to alcoholic steatohepatitis, marked by liver inflammation, hepatocyte injury, and ballooning degeneration. Prolonged alcohol intake promotes persistent inflammation and fibrosis, eventually leading to cirrhosis, which significantly increases the risk of HCC ().

Alcohol consumption triggers the activation of the NLRP3 inflammasome in Kupffer cells, which in turn activates caspase-1 and induces the release of IL-1β, exacerbating inflammation and liver damage (). Additionally, alcohol-induced ROS production via CYP2E1 leads to mitochondrial dysfunction and oxidative stress, compromising liver regeneration and contributing to hepatocyte damage (). Reactive nitrogen species (RNS), particularly peroxynitrite, further contribute to liver damage through nitrosative stress (). Alcohol-induced disruptions in lipid metabolism also play a pivotal role in developing ALD by altering the NAD+/NADH ratio and impairing mitochondrial β-oxidation of fatty acids, which causes triglyceride accumulation in the liver (Figure 3) (). This metabolic imbalance is exacerbated by increased expression of sterol regulatory element-binding protein 1, a key regulator of lipid biosynthesis, and reduced activity of PPARα, a transcription factor essential for fatty acid oxidation (). Moreover, alcohol-induced gut dysbiosis and increased intestinal permeability allow bacterial endotoxins to enter the liver, amplifying inflammation and hepatic damage ().

These intersecting mechanisms highlight the severe, multi-faceted nature of ALD. While alcohol moderation is often discussed as a preventive measure, substantial evidence indicates that toxic effects are present even at low to moderate levels of consumption (; ). Furthermore, liver damage such as mitochondrial dysfunction can persist even after extended periods of abstinence, suggesting that recovery is neither immediate nor guaranteed (). Therefore, the most effective strategy to prevent the initiation and progression of ALD is the avoidance of alcohol. For individuals with existing damage, therapeutic approaches aimed at mitigating oxidative stress and cellular injury are being actively investigated ().

3.2 Type 2 diabetes mellitus (T2DM)

Excessive alcohol consumption is a known contributor to both the onset and progression of T2DM due to its detrimental impacts on insulin secretion and sensitivity. Alcohol impairs pancreatic β-cell function, reducing basal insulin secretion and increasing β-cell apoptosis (; ). This β-cell dysfunction, combined with alcohol-induced insulin resistance in the liver and skeletal muscle, disrupts glucose homeostasis, a hallmark of early-stage T2DM (). Alcohol also interferes with glycogenolysis and gluconeogenesis, essential for maintaining blood glucose levels, which increases the risk of abnormal blood glucose regulation and hypoglycemia (; ). In the liver, alcohol activates hypoxia-inducible factor 1 (HIF-1), which upregulates glucose transporter 1, leading to increased glucose uptake and potential glucose toxicity (; ).

Additionally, alcohol-induced dysregulation of key metabolic hormones, such as ghrelin and leptin, further contributes to the pathogenesis of T2DM. Ghrelin, a hormone that stimulates insulin secretion, is disrupted in T2DM patients who consume alcohol excessively, leading to increased hepatic glucose production and reduced peripheral glucose utilization (). Leptin, which normally suppresses ghrelin and regulates glucose metabolism, is also dysregulated, exacerbating insulin resistance and glucose intolerance (). Ethanol and its toxic metabolites accumulate in pancreatic tissues, causing cellular damage and inflammation, potentially leading to acute and chronic pancreatitis. The production of FAEEs during non-oxidative ethanol metabolism is particularly toxic to pancreatic cells, disrupting cellular membranes, promoting calcium overload, and inducing cell death, further contributing to alcoholic pancreatitis (; ). Reduced insulin production diminishes the ability of the pancreas to maintain glucose homeostasis, worsening systemic effects such as hyperglycemia and insulin resistance, which exacerbate the metabolic complications of chronic alcohol consumption ().

Taken together, these mechanisms indicate that excessive alcohol consumption accelerates both the development and severity of T2DM by impairing insulin function, altering glucose metabolism, and disrupting key metabolic hormones. These combined mechanisms underscore alcohol’s significant role in promoting T2DM progression and complications.

3.3 Cardiovascular disease (CVD)

The relationship between alcohol consumption and cardiovascular health is complex. Moderate alcohol intake has been associated with protective effects, including increased high-density lipoprotein (HDL) cholesterol levels, improved endothelial function, and reduced platelet aggregation that may lower the risk of coronary artery disease and atherosclerosis (; ). However, these potential benefits are not attributed to all alcoholic beverages but are primarily linked to moderate red wine consumption, largely due to its high content of beneficial polyphenols (). Furthermore, this association is often observed in the context of broader healthy lifestyle patterns, such as the Mediterranean diet, making it difficult to isolate the effects of red wine alone (). The evidence remains debated, and further research is required to fully elucidate the specific cardiovascular benefits of red wine and its components ().

In contrast, excessive alcohol intake significantly elevates the risk of CVDs, such as alcohol-induced cardiomyopathy, characterized by reduced myocardial contractility, cardiac hypertrophy, and interstitial fibrosis (Figure 2) (; ). Chronic alcohol consumption disrupts lipid metabolism, raising low-density lipoprotein cholesterol and triglyceride levels, thereby contributing to atherosclerosis and hypertension (). Additionally, excessive alcohol consumption elevates blood pressure and promotes vascular endothelial dysfunction, oxidative stress, and inflammation, all of which contribute to the development of CVDs (). The production of acetaldehyde and ROS in cardiac myocytes induces oxidative stress, mitochondrial dysfunction, and inflammation. These processes compromise structural and functional integrity of heart cells, impairing ATP production, disrupting calcium handling, and triggering apoptosis ().

In addition, ethanol metabolism in the heart alters lipid metabolism, promoting dyslipidemia and fat accumulation within cardiac tissues by interfering with the regulation of lipid-modulating transcription factors, such as peroxisome proliferator-activated receptors (PPARs) (). This lipid imbalance, along with the oxidative damage, accelerates the development of atherosclerosis and coronary artery disease. Chronic alcohol consumption also raises circulating catecholamine levels, leading to vasoconstriction and increased blood pressure, which heightens the risk of hypertension, stroke, and other cardiovascular complications (). Cardiac dysrhythmias, such as atrial fibrillation, are also common in individuals who consume alcohol excessively, further compounding their cardiovascular risk ().

Several genetic factors can influence individual susceptibility to alcohol-related cardiovascular damage. Variants of ADH and ALDH, such as ADH1B and ALDH2*2, alter the metabolism of alcohol and acetaldehyde, potentially increasing cardiovascular risks in certain populations (). In summary, while moderate alcohol consumption may provide certain cardiovascular benefits, excessive intake overwhelmingly disrupts cardiovascular health, underscoring the critical balance needed to prevent alcohol-induced CVD.

3.4 Obesity and malnutrition

Alcohol’s high caloric content (7 kcal/g) can contribute to weight gain and obesity, especially in heavy drinkers. Beyond caloric intake, alcohol affects several metabolic pathways that promote fat accumulation, particularly in the liver and other peripheral tissues (; ). Chronic alcohol consumption enhances lipolysis in adipose tissue, increasing circulating free fatty acids (FFAs), which are subsequently stored in the liver as triglycerides, contributing to alcoholic fatty liver disease (; ). Ethanol metabolism significantly impacts adipose tissue by increasing lipolysis, altering hormone regulation, and promoting insulin resistance, leading to greater release of FFAs into the bloodstream (). Alcohol also disrupts the regulation of hormones involved in fat metabolism, such as adiponectin, leptin, and resistin (). A primary target of this disruption is adiponectin, a hormone that promotes fatty acid oxidation, exerts anti-inflammatory effects, and improves insulin sensitivity (). By suppressing the secretion and reducing plasma levels of adiponectin, alcohol triggers a cascade of metabolic dysfunctions, including impaired glucose tolerance, insulin resistance, and elevated circulating FFAs, which collectively exacerbate hepatic lipotoxicity and worsen obesity-related metabolic disorders (). Alcohol-induced upregulation of the microsomal ethanol-oxidizing system (MEOS), primarily involving CYP2E1, reduces fat utilization, favoring fat storage and further increasing the risk of obesity (; ).

Conversely, significant weight loss and malnutrition are also frequently observed, particularly in individuals with severe alcohol use disorder. This paradox is often linked to alcohol-associated disordered eating patterns, where alcoholic calories substitute for nutritious food. This disruption primarily occurs at the brush border membrane of the small intestine, where alcohol alters the transport of nutrients like glucose, amino acids, vitamins, and minerals (). Ethanol disrupts the structural integrity of intestinal cells, reduces villus height, and affects transporter proteins, leading to increased intestinal permeability and decreased absorption efficiency (). This compromised intestinal barrier not only leads to malabsorption but also exacerbates systemic inflammation by allowing bacterial endotoxins to translocate into the bloodstream, further driving metabolic dysfunction. Additionally, alcohol’s low nutritional value and substitution for food contribute to deficiencies, cellular damage, and metabolic imbalances (). Chronic alcohol consumption can also modulate the hypothalamic-pituitary-adrenal axis, affecting hunger signals and reducing appetite, particularly for carbohydrate-rich foods (; ). These combined effects impair digestion and promote a negative energy balance, exacerbating malnutrition and health complications ().

Genetic factors can also play a role, as evidenced by the ADH1B gene variant (rs1229984), which has been linked to significant weight gain in individuals who consumed alcohol, further highlighting the genetic susceptibility to alcohol-induced obesity (). Taken together, these findings highlight alcohol’s paradoxical and damaging role in energy balance, contributing to obesity in some while causing severe malnutrition in others, often in the context of disordered eating. Therefore, limiting alcohol consumption is crucial for reducing both health risks and its associated metabolic complications.

3.5 Neurological damage

Ethanol metabolism significantly affects the brain as alcohol can cross the blood-brain barrier () and be metabolized locally (Figure 2). Acetaldehyde exerts neurotoxic effects, such as impaired synaptic function and neuronal apoptosis, by forming adducts with proteins and DNA that disrupt cellular processes (; ). Chronic ethanol exposure disrupts brain energy metabolism, leading to reduced glucose uptake and impaired mitochondrial function in neurons. These energy deficits, along with excessive ROS production, contribute to neurodegenerative conditions, including alcohol-related dementia and Wernicke-Korsakoff syndrome (; ).

Beyond direct toxicity from its metabolites, a central mechanism of alcohol-induced brain injury is the induction of a persistent neuroinflammatory state. While chronic alcohol use is known to activate microglia, it also triggers a reactive response in other glial cells like astrocytes. This widespread glial activation results in the release of a barrage of pro-inflammatory cytokines (e.g., TNF-α, IL-1β), chemokines, and additional ROS within the brain. This sustained neuroinflammation, driven by oxidative stress, damages neurons, disrupts synaptic plasticity, and is now understood to be a key driver of the cognitive deficits and emotional dysregulation characteristic of alcohol use disorder ().

Moreover, alcohol disrupts neurotransmitter balance, with effects varying by brain region and neuronal cell type, by enhancing gamma-aminobutyric acid (GABA) activity and inhibiting glutamate signaling, leading to impairments in mood regulation, memory, and motor coordination (). Over time, the combined insults of direct toxicity, oxidative stress, persistent neuroinflammation, and widespread neurotransmitter dysregulation impair synaptic plasticity, reduce cognitive function, and lead to significant neuronal loss and brain atrophy ().

3.6 Alcoholic myopathy and muscle wasting

In addition to the organ systems discussed, ethanol exerts adverse effects on skeletal muscle by suppressing the mammalian target of rapamycin (mTOR) signaling, leading to reduced muscle protein synthesis () and activating the ubiquitin-proteasome pathway for muscle protein degradation (). Additionally, its metabolites, e.g., acetaldehyde and acetate, further disrupt glucose and fatty acid metabolism (). In skeletal muscle, acetate derived from ethanol metabolism is converted into acetyl-CoA and enters the TCA cycle for energy production ().

Chronic alcohol consumption reduces insulin sensitivity by impairing the activation of key proteins in insulin signaling, such as insulin receptor substrate-1 (IRS-1) and AKT, leading to reduced glucose uptake in muscle cells (). This disruption is further exacerbated by oxidative stress and pro-inflammatory cytokines, which interfere with normal insulin signal transduction and promote insulin resistance. The resulting decrease in glucose utilization leads to muscle wasting, a hallmark of alcoholic myopathy, characterized by muscle weakness, atrophy, and loss of muscle mass (). Chronic alcohol exposure also inhibits protein synthesis by suppressing the mTOR pathway and increases protein degradation through the activation of the ubiquitin-proteasome system, involving muscle-specific E3 ubiquitin ligases, such as muscle ring finger 1 and atrogin-1, leading to muscle wasting (). In addition, increased production of ROS in muscle, often driven by impaired mitochondrial function by chronic alcohol exposure, further damages muscle fibers and reduces ATP production, limiting muscle endurance and performance and causing structural damage, particularly in fast-twitch muscle fibers ().

4 Summary and future directions

This review has highlighted the extensive detrimental effects of excessive alcohol consumption across multiple organ systems. These harmful effects stem from alcohol’s toxicity, its promotion of oxidative stress, and the substantial reduction in the NAD+/NADH ratio. Alcohol and its metabolites disturb the regulation of lipid and glucose metabolism, increasing the production of ROS and RNS, which further drives oxidative stress and inflammation, ultimately leading to cellular and organ damage. These interconnected pathways not only drive a range of chronic diseases, including liver disease, CVD, T2DM, and obesity, but also provide a clear roadmap for developing targeted therapeutic strategies.

While abstinence is paramount, emerging approaches aim to target the core mechanisms of injury. Promising pharmacological strategies include blocking inflammatory cell recruitment with chemokine receptor antagonists. Furthermore, nutritional and metabolic interventions counteract alcohol-induced damage. Supplementation with NAD+ precursors like nicotinamide riboside (NR) or nicotinamide mononucleotide (NMN) helps replenish the depleted NAD+ pool, while therapies targeting the gut-liver axis, such as probiotics or fecal microbiota transplantation work to repair intestinal barrier function and reduce systemic inflammation.

Ultimately, the shared mechanisms of oxidative stress, inflammatory responses, mitochondrial dysfunction, and metabolic disruption demonstrate alcohol’s systemic impact. This mechanistic overlap underscores the systemic risks posed by excessive alcohol consumption and emphasizes that reducing alcohol consumption is the safest strategy to mitigate the broad spectrum of alcohol-related health complications.

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Author contributions

JL: Visualization, Writing – original draft. J-YL: Conceptualization, Writing – review and editing. HK: Conceptualization, Writing – original draft.

Funding

The author(s) declare that financial support was received for the research and/or publication of this article. This research was supported by the National Research Foundation of Korea (NRF) (No. RS-2025-16068795), funded by the Ministry of Science and ICT.

Conflict of interest

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

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All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.

Glossary

  • ACS

    acetyl-CoA synthetase

  • ADH

    alcohol dehydrogenase

  • AFL

    alcoholic fatty liver

  • ALD

    alcohol-related liver disease

  • ALDH

    aldehyde dehydrogenase

  • acetyl-CoA

    acetyl coenzyme A

  • CCL2

    chemokine (C-C motif) ligand 2

  • CYP2E1

    cytochrome P450 2E1

  • FAEE

    fatty acid ethyl esters

  • FFA

    free fatty acid

  • GI

    gastrointestinal

  • IL-1β

    interleukin-1β

  • IL-6

    interleukin-6

  • LDH

    lactate dehydrogenase

  • LPS

    lipopolysaccharide

  • mtDNA

    mitochondrial DNA

  • NAMPT

    nicotinamide phosphoribosyltransferase

  • NAD+

    nicotinamide adenine dinucleotide

  • NADH

    a reduced form of nicotinamide adenine dinucleotide

  • NADPH

    nicotinamide adenine dinucleotide phosphate

  • NF-κB

    nuclear factor kappa-light-chain-enhancer of activated B cells

  • NLRP3

    NOD-like receptor family pyrin domain containing 3

  • PPAR

    peroxisome proliferator-activated receptor

  • RNS

    reactive nitrogen species

  • ROS

    reactive oxygen species

  • SCFA

    short-chain fatty acid

  • SIRT1

    sirtuin 1

  • TCA

    tricarboxylic acid

  • T2DM

    type 2 diabetes mellitus

  • TLR4

    toll-like receptor 4

  • TNF

    tumor necrosis factor

  • UPRmt

    mitochondrial unfolded protein response.

References

Summary

Keywords

alcohol, metabolic dysfunction, inflammation, alcohol-related disease, oxidative stress

Citation

Lee J, Lee J-Y and Kang H (2025) Excessive alcohol consumption: a driver of metabolic dysfunction and inflammation. Front. Toxicol. 7:1670769. doi: 10.3389/ftox.2025.1670769

Received

22 July 2025

Accepted

16 September 2025

Published

29 September 2025

Volume

7 - 2025

Edited by

Parames C. Sil, Bose Institute, India

Reviewed by

Jose Manuel Lerma-Cabrera, University of Almeria, Spain

Robert Wade Siggins, Louisiana State University, United States

Updates

Copyright

*Correspondence: Hyunju Kang,

Disclaimer

All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article or claim that may be made by its manufacturer is not guaranteed or endorsed by the publisher.

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